U.S. Pat. Nos. 3,567,189 and 3,704,896 show auxiliary axles for trucks having castered wheels. With reference to the latter patent, hydraulic damping of the castered wheels is commonly provided.
In a hydraulic damping system however, the degree of damping varies with the velocity of the motion being damped and thus such systems serve to prevent some wheel fluttering but no more. Additionally, such systems are not at all adapted to being adjustable.
It has been discovered that a frictional damping device which is readily adjustable also dependably provides a remarkable degree of directional stability in the operation of the vehicle, provided that such adjustment is properly correlated with the amount of the load of the particular vehicle and its operating characteristics.
It is an object of the invention to provide a suitable automatic adjustment of such damping; to provide the same in a compact, sturdy inexpensive, accessible assembly; to provide the same with an added damping having a fixed rate which is adjustable and which upon adjustment thereafter remains fixed.
U.S. Pat. No. 3,877,715 of another and Earl C. Thayer who is the joint inventor here shows a typical hydraulic system for operating a rear auxiliary axle with castered wheels. The present invention is particularly adapted to utilizing the hydraulic pressure available in such a system.